<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      let animal = {
        jumps: null,
      };
      let rabbit = {
        __proto__: animal,
        jumps: true,
      };
      console.log(rabbit.jumps); // true
      delete rabbit.jumps;
      console.log(rabbit.jumps); // null
      delete animal.jumps;
      console.log(rabbit.jumps); // undefind
    </script>
  </body>
</html>
